Lubricant compositions



United States Patent Office 3,309,314 Patented Mar. 14, 196? 3,309,314LUBRICANT COMPOSITIONS James R. Price, Robert C. Spillman, and KennethT.

Wendler, all of Alton, Ill., assignors to Shell Oil Company, New York,N.Y., a corporation of Delaware No Drawing. Filed May 29, 1964, Ser. No.371,184

6 Claims. (Cl. 252--32.5)' I This invention relates to improvedsynthetic lubricating compositions which are oxidation-stable andnon-corrosive, and which have excellent extreme-pressure and antiwearproperties.

Recently, synthetic lubricants have gained prominence in the field oflubrication because of stringent requirements of certain newapplications. These lubricants, which are frequently esters, ethers,silicones, or hydrocarbon polymers, are generally designed, and may betailored for special applications where conventional mineral oils arenot satisfactory. Synthetic lubricants have low pour points anddesirable viscosity characteristics, and can generally be used attemperatures considerably above the decomposition temperatures of mostmineral oils. Accordingly, these oils have found use in jet aircraft,missiles, automatic Weapons, etc., Where wide temperature ranges andextreme operating conditions are likely to be encountered. Properlubrication of aircraft gas turbines, for example, requires ability tofunction at bulk oil temperatures as low as -65 F. to as high as 450 to500 F. for some applications.

Under the extreme conditions to which these lubricants are subjected,synthetic oils are often corrosive and undergo thermal and oxidativedeterioration resulting in sludge and deposit formation, viscositychange, discoloration, and other undesirable changes. Attempts tocorrect these deficiencies by conventional methods are oftenunsatisfactory because of the extreme nature of the application of theoil; for example, addition of an antioxidant to reduce deterioration maycause increased corrosion, or addition of an an antiwear agent mightdecrease stability. Furthermore, attempts to remedy the new deficienciesfrequently compound the problem by causing increased sludging, etc.Therefore, available information regarding mineral oil formulations isof little aid in developing successful synthetic lubricants.

It has now been discovered that synthetic lubricants containing 1) 0.01to by weight of a C to C oilsoluble aliphatic amine salt of a monotoper-haloalkyl phosphonic acid, the haloalkyl radical of which contains 1to 4 carbon atoms, and (2) 0.01 to 10% by weight of a primary totertiary amine of which each non-hydrogen substituent is a monotodi-nuclear unsaturated cyclic radical containing from 4 to 10 carbonsand from 0 to 2 nitrogens, have excellent antiwear, oxidation andanticorrosion properties. The term unsaturated cyclic radical usedherein includes radicals of heterocyclic groups salt (hereinafter alsocalled the salt) and the cyclic amine exhibit surprising oxidationstability, non-corrosivity, and cleanliness.

THE ADDITIVE COMBINATION Aryl amines are, of course, well known aslubricating oil oxidation inhibitors. Although phosphonic acid-aminesalts are known antiwear additives, they are not known to increaseoxidation stability; indeed, these salts do not, by themselves, haveantioxidant properties. It has now been found, however, that these saltscooperate with cyclic amine antioxidants to produce increased oxidationresistance. This effect is illustrated in Table I, below, whichillustrates the results of an air oxidation test conducted at 400 F. Airwas passed at a rate of ml./ min. through a 20-gram sample whichcontained 20 ppm. copper and 20 p.p.m. iron (as soluble octoates) ascatalysts. The base stock, designated -Oil E, consisted of about 60% CC, 'alphatic-acid esters of pentaerythritol and about 40% C C aliphaticacid esters of dipentaerythritol.

TABLE I.--RESULTS OF 400 F. AIR OXIDATION TEST l Salt A is a mixed saltof monochloromethyl phosphonic acid and a mixture oftert-O1aCna1ky1primary amines.

The data in Table I illustrate the cooperative effect of anamine-phosphonic acid salt and a cyclic amine antioxidant in promotingoxidation stability of a synthetic base oil. The introduction period ofthe cyclic-aminestabilized base is almost doubled by addition of thesalt, which is shown to be ineffective, independent of the cyclic amine,as an oxidation inhibitor.

Further evidence of beneficial effects attributable to the presence ofthe cyclic amine-salt combination of the invention is evidenced in theoxidation-corrosion test results in Table II. Oil B (about C -Caliphatic acid esters of pentaerythritol, 5% C -C aliphatic aicd estersof dipentaerythritol), was subjected alone, andwith the additives of theinvention individually and in combination, to a test similar to thatdescribed in Federal Test Method Standard No. 791a as method 5308.4.Fluid samples cc.) were heated at a temperature of 450 F. for 72 hoursin the presence of 1.0 square inch of each of the metals listed in thetable. Air was bubbled through the sample at the rate of 5 liters perhours. Corrosion was measured in weight loss per unit of surface area.

TABLE II.-RESULTS OF CORROSION-OXIDATION TESTS AT 450 F. V

Corrosion, mg./cm. Viscosity Run Formulation Acid No. (100 F.) IncreaseIncrease, Mg Al Cu Fe Ag Percent Oil B --19.7 +0.02 0.l3 26.9 +0.07 17.1Solid Oil B plus 1% 2,2dipyridylamine 3.61 +0.08 0.30 +0.18 +0.14 8.815.8 Oil B plus 1% salt A 1 l7.35 +0.04 1.55 +0.05 +0.14 38.9 379 Oil Bplus 1% 2,2-dipyridylamine plus 0.1% sa1tA 0.45 +0.30 0.13 +0.17 +0.270.1 9.9

1 Salt A" is a mixed salt of monochloromethyl phosphonic acid and amixture or tart-01543 alkyl primary amines.

such as pyridine, quinoline, and diazine as well as aryl radicals suchas benzene and naphthalene. These amines will be referred to herein ascyclic amines. Lubricants containing the combination of theamine-phosphonic acid Several conclusions are apparent from theseresults. Rather severe corrosion of iron, copper, and/or magnesium isexperienced in the synthetic base in the absence of any additive, orwhen either the cyclic amine or salt additive is present alone. In thepresence of both the cyclic amine and salt additives,however,corrosivity of all of the metals is considerably reduced. Lowcorrosivity to a number of different metals is essential for someapplications, for instance, jet aircraft turbine lubrication, where theoil contacts parts made from a variety of metals and alloys. Also,presence of corrosion products may be detrimental to the stability ofthe oil, and accellerates degradation and decomposition.

As well as illustrating the excellent corrosion-inhibiting propertiescompositions of the invention, the data in Table II also provide furtherillustration of the enhanced oxidation resistance of these mixtures. Theincreases in acidity and viscosity, which are qualitative measures ofstability, are considerably lower for the oil containing the cyclicamine-salt combination than for the oil containing no additive or onlyone of the additives of the combination.

Oils containing the cyclic amine-salt combination of the invention alsohave a particular advantage in exhibiting extremely low lead (Pb)corrosion. In the past, synthetic lubricants containing cyclic amineantioxidants have generally been corrosive to lead, in the absence oflead-corrosion inhibitors such as2,6-di-tert-butyl-4-dimethylamine-p-cresol. Lead is corroded much moreeasily than other metals, such as steel, aluminum, magnesium, copper,and silver; also, lead corrosion is not predictable from corrosionresults of other metals. The difference of the lead corrosion functionfrom the normal corrosion function is apparent from a comparison of Run3 in Table III, below, with Run 2 in Table II. These results show thatin a pentaerythritol ester oil, 2,2-dipyridylamine acts generally as acorrosion inhibitor for most metals, but promotes lead corrosion.Indeed, many other additives which are known to be corrosion inhibitorsin other applications have been found to be ineffective for inhibitinglead corrosion.

The lead corrosion induced by the cyclic amines is substantiallyeliminated by addition of the phosphonic acid-amine salt. This isevidenced in Table III below, which shows the results of lead-corrosiontests for Oil B (the pentaerythritol ester base described before TableII) alone, Oil B with cyclic amine antioxidants, and Oil B with theamine-salt combination of the invention. These oils were subjected tothe MacCoull-Ryder test and the SOD lead corrosion test. TheMacCoull-Ryder test was run for five hours at 325 F; this test isdescribed in detail SAE Journal 50, 8, p. 338 (Aug. 1942). In the SODlead corrosion test, rapidly rotating panels of lead and copper wereheated in the oil sample for one hour at 325 F. while air was bubbledthrough the sample; this test is described in detail in Federal TestMethod Standard No. 791a Method 5321.1. The compositions tested andresults obtained are presented in Table III below.

TABLE TIL-RESULTS OF LEAD-CORROSION TESTS each non-hydrogen substituentof which is a monoto dinuclear unsaturated cyclic radical containingfrom 4 to 10 carbon atoms and from 0 to 2, preferably 0 to l nitrogenatoms. Primary to secondary, especially secondary, amines are preferred;the cyclic radicals are preferably aromatic. Included are aryl aminesand amines having nitrogen-containing heterocyclic substituents. Many ofthese amines are well known antioxidants for both synthetic and minerallubricating oils. Examples of suitable aryl amines arephenyl-u-naphthylamine, phenyl-B-naphthylamine, diphenylamine,di-u-naphthylarnine, di-fi-naphthylamine, di-u,;8-napl1thylamine,triphenylamine, and diphenyl naphthylamine. Examples of suitable amineshaving a nitrogen-containing heterocyclic constituent are dipyridylamines, aminopyrides, aminoquinolines, etc. Specific examples include2,2'-dipyridylamine, 2-aminopyridine, 3-an1inopyridine, 4-aminopy1idine,2,6-diaminopyridine, 4-4 dipyridylamine, phenyl 2 pyridylaminenaphthyl-Z-pyridylamine, 3-aminoquinoline, and phenyl- 3-quinolylamine.Preferred amines are phenyl-a-naphthylamine, diphenylamine,2-2'dipyridylamine and the aminopyridines. The cyclic amines are used inamounts of from 0.01 to 10% by weight, preferably 0.025% by weight ofthe final lubricating composition.

THE SALT The salt to be used in combination with the cyclic aminedescribed above is a salt of (D -C alkylamine and a monoto per-haloalkylphosphonic acid, the haloalkyl group containing 1 to 4, preferably 1 to2 carbon atoms. The haloalkyl phosphonic acids used for preparing thesalts for use in the invention generally have the formula where R ismonoto per-haloalkyl containing 1 to 4, preferably 1 to 2 carbon atoms.R preferably contains 1 to 2 halogen atoms, more preferably 1 chlorineatom; it is also preferred to have at least one of the halogenssubstituted on the alpha carbon atom. Preferred halogens are fluorine,chlorine, and bromine, especially chlorine. Examples of suitablephosphonic acids are monochloromethylphosphonic acid,1-monochloroethylphosphonic acid, 1,1 dichloropropylphosphonic acid,perchloroethylphos phonic acid, dichloromethylphosphonic acid,perchlorornethylphosphonic acid, monobromomethylphosphonic acid,1,1-chlorobromopropylphosphonic acid, dibromomethylphosphonic acid,Inonofluoromethylphosphonic acid, and 1,l-difiuoroethylphosphonic acid.

Amines which form effective salts of the phosphonic acids are primary tosecondary alkyl amines having at least 8, preferably 8 to 30, and morepreferably 12 to 24 carbon atoms per molecule. Branched tertiary-alkylprimary amines are preferred; branched in this context 1 About 04-01alkanoic acid esters of pentaerythritol, 5% 05-010 alkanoic acid estersof dipentaerythritol.

From these results it is apparent that the high lead corrosion inducedby the cyclic amine is completely inhibited by the phosphonic acid-aminesalt.

THE CYCLIC AMINE Suitable cyclic amines to be used in the amine-saltcombination of the invention are primary to tertiary amines,

means having at least 2 hydrocarbon substituents attached to the maincarbon chain. As the tertiary-alkyl radical, the radical ofpolyisobutylene and polypropylene, and mixtures of these areparticularly preferred. Examples of these amines are1,1,3,3-tetramethylbutylamine, 1,1,3, 3,5,5 hexamethylhexylamine,1,l,3,3,5,5,7,7-octamethyloctylamine, and1,1,3,3,5,5,7,7,9,9-decamethyldecylamine.

Tertiary alkyl methyl primary amines, such as 2,2,4,4-tetramethylpentylamine and 2,2,4,4,6,6-hexamethyl hexylamine are alsosuitable.

Other primary amines having 8 to 30 carbons which are appropriate forforming the salts of the invention are described in Bortnick, US.2,606,923, issued Aug. 12, 1952, and Bortnick, US. 2,611,782, issuedSept. 23, 1952. These include tert-tridecylamine,

as Well as isoheptyl diethyl carbinylamine, isooctylethylpropylcarbinylamine, etc. Primary amines of this type are commerciallyavailable from Rohm and Haas Company under the trade name of Primenes.The amine may also be a polyamine, such as a diamine or triamine, andmay contain other non-reactive groups, such as amide or ether groups, inthe carbon chain.

Some specific examples of secondary amines for making the phosphonicacid salts are diamylamine, dihexylamine, di(2-ethylhexyl)-amine,dioctylamine, didecylamine, didodecylamine, ditetradecylamine,dihexadecylamine, dioctadecylamine, dibromodioctadecylamine,isopropyloleylamine, diricinoelylamine, butylricinoleylamine, butyl-2-ethylhexylamine, dilaurylamine, methyloleylamine, ethyloctaylarnine,isoamylhexylamine, dicyclohexylamine, dicyclopentylamine,cyclohexyloctylamine, cyclohexylbenzylamine, benzyloctylamine,benzyl-2-ethylhexylamine, allyloctylamine, dodecyl-2-ethylhexylamine,(1-isobutyl-3- methylbutyl)-3,3,3-methylcyclohexylamine, di( l-isobutyl-3-methylbutyl)-amine; N-n-dodecyldiethylenetriamine, N-n-tetradecyldiethylenetriamine, octylethylene diamine, N- 2-ethylhexylN-hexadecyl triethylene tetramine, heptyl trimethylene diamine,N-tetradecyl tripropylene tetramine, N,N-diallyl trimethylene diamine,3-hexyl-morpholine, and the like.

The phosphonic acid-amine salts for use in the invention can be preparedby direct neutralization of haloalkylphosphonic acid with asubstantially stoichiometric amount of amine. The reaction occurs atnormal or moderately elevated temperatures and may be carried out in thepresence of an inert diluent or solvent, such as a hydrocarbon, alcohol,ether, ketone, etc. Preparation of these salts is described in Watson etal., U.S. 2,858,332, issued Oct. 28, 1958.

The phosphonic acid-amine salts useful in the invention may also bemodified with an alkali metal as described in Price et al., US.3,112,267, issued Nov. 26, 1963. The full amine salt of the phosphonicacid is prepared and is then treated in a low-boiling solvent with analkali metal hydroxide, carbonate, or alcoholate such that one of theamine groups is replaced with an alkali metal. Preferred alkali metalsare sodium, potassium, and lithium.

The amine-phosphonic acid salts are used in amounts of from about 0.005to 5% by weight, preferably about 0.01 to 5% by weight of thelubricating composition.

Weight ratios of the amount of salt to the amount of cyclic amine usedin the combination of the invention are from about 0.01/1 to about /1,preferably from about 0.1/1 to about 5/1. The combination may be addedas a package to lubricating oils.

THE BASE OIL The additive combination of the invention is appropriate inmineral as well as synthetic lubricating oils, but is particularlyuseful in synthetic oils which are used under more extreme conditionswhere the particular advantages of the additives of the invention becomemore pronounced. Synthetic lubricants suitable for the invention are ofvarious types, such as aliphatic esters, silicones, polyalkylene oxides,polyphenyl ethers, fiuorinated hydrocarbons, polyolefins, and phosphateesters. Examples of silicones include methyl silicone, methylphenylsilicone, methylchlorophenyl silicone, etc. Examples of polyalkyleneoxides 6 are polyisopropylene oxide, polyisopropylene oxide diether, andpolyisopropylene oxide diester. Fluorinated hydrocarbons includefluorinated oils and perfluorinated hydrocarbons.

Preferred synthetic lubricant base stocks are esters of alcohols having1 to 20, especially 4 to 12, carbon atoms and aliphatic carboxylic acidshaving from 3 to 20, especially 4 to 12, carbon atoms. The ester basemay be a simple ester (reaction product of a monohydroxy alcohol and amonocarboxylic acid), a polyester (reaction product of an alcohol and anacid, one of which has more than one functional group), or a complexester (reaction product of a polyfunctional acid with more than onealcohol, or of a polyfunctional alcohol with more than one acid). Also,excellent synthetic lubricants may be formulated from mixtures ofesters, such as major proportions of complex esters and minor amounts ofdiesters.

Monohydric alcohols suitable for making ester base stocks includemethyl, h-utyl, isooctyl, dodecyl and octadecyl alcohols. OX0 alcoholsprepared by the reaction of olefins with carbon monoxide and hydrogenare suitable. Neo alcohols, i.e., alcohols having no hydrogens on thebeta carbon atom are preferred. Examples of such alcohols are2,2,4-trimethylpentan-ol-1 and 2,2-dimethyl propanol.

Polyalcohols used for the production of base oil esters preferablycontain 1 to 12 carbons. Examples of dialco- 11015 are2-ethyl-l,3-hexanedi0l, 2-propyl-3,3-heptanedi0l,2-butyl-l,3-butanediol, 2,4-d-imesityl-1,3-butanediol, and polypropyleneglycols having molecular Weights of from about 100 to 300. Alcoholshaving 3, 4, 5 or more bydroxyl groups per molecule are also suitableand are preferred; examples of these polyols are pentaerythritol,dipentaerythritol, and trimethylolpropane. Mixtures of alcohols may alsobe used.

Suitable carboxylic acids for making the ester base oils include monoanddi-basic aliphatic carboxylic acids. Examples of appropriate acids arebutyric, valeric, sebacic, azelaic, suberic, succinic, caproic, adipic,ethyl suberic, diethyl adipic, oxalic, malonic, glutaric,pentadecanedicarboxylic, diglycolic, thiodiglycolic, acetic, propionic,caprylic, lauric, palmitic, pimelic, and mixtures thereof. Preferredacids are sebacic, azelaic, glutaric, adipic, and their mixtures.

Examples of suitable ester base oils are ethyl palmitate, ethyl laurate,butyl stearate, di(2-ethylhexyl) sebacate, di-(Z-ethylhexyl) azelate,ethyl glycol dilaurate, di-(2- ethylhexyl) phthalate,di-(1,3-methylbutyl) adipate, di- (l-ethylpropyl) azelate,diisopro-pyloxylate, dicyclohexyl sebacate, glycerol tri-n-heptoate,di(undecyl) azelate, and tetraethylene glycol di-(2-ethylene caproate),and mixtures thereof. An especially preferred mixture of esters consistsof about 50 to wt. bis(2,2,4-trimethylpentyl) azelate and 20 to 50% wt.1,1,1-trimethylyl propane triheptano-ate.

Especially preferred esters for use as base stocks in the presentinvention are esters of monocar-boxylic acids having 3 to 12 carbons andpolyalcohols such as pentaerythritol, dipentaerythritol, andtrimethylolpropane. Examples of these esters are pentaerythritylbutyrate, pentaerythrityl tetrabutyrate, pentaerythrityl tetravalerate,pentaerythrityl tetracaproate, pentaerythrityl dibutyra-tedicaproate,pentaerythrityl butyratecaproate divalerate, pentaerythrityl butyratetrivalerate, pentaerythrityl butyrate tricaproate, pentaerythrityltributyratecaproate, mixed C saturated fatty acid esters ofpentaerythritol, dipentaerythrityl hexavalerate, dipentaerythritylhexacaproate, dipentaerythrityl hexaheptoate, dipentaerythritylhexacaprylate, dipentaerythrityl tributyratecaproate, dipentaerythrityltrivalerate trinonylate, dipentaerythrityl mixed hexaesters of C fattyacids and trimethylolpropane heptylate. Pentaerythritol esters ofmixtures of C -C acids are excellent base oils, and are commerciallyavailable from Hercules Chemical Company.

Ester oils may be prepared by simple reaction of the Composition 1 BaseA:

60% W. bis(2,2,4-trimethylpentyl)azelate 40% W. 1,1,1-trimethylylpropane triheptanoate +1% W. phenyl ounaphthylarnine +02% W. salt ofmixed C C primary amines and monochloromethyl phosphoric acidComposition 2 Base B:

60% W. C C; acid esters of pentaerythritol 40% W. (Dy-C acid esters ofdipentaerythritol +1% W. diphenylamine -+0.2% W. salt of mixed C Cprimary amines and monochloromethyl phosphonic acid Composition 3 Base Bl-1% w. 2,2-diphyridylamine+0.2% w. salt of mixed O -C primary aminesand monochloromethylphosphonic acid Composition 4 Base A+1%4-aminopyridine+0.2% W. salt of Chg-"C24 mixed primary amines and1,1-d-ichloroethylphosphonic acid Composition 5 Base B+1%diphenylamine+0.2% w. salt of Gig-C24 mixed primary amines andmonochloromethylphosphonic acid We claim as our invention:

1. A lubricant composition comprising a major amount of a syntheticester lubricating oil and (1) 0.01 to 5% by Weight of a salt of an alkylamine selected from the group consisting of alkyl primary and alkylsecondary amines having from 8 to 30 carbon atoms and a monotoper-haloalkyl phosphonic acid, wherein the haloalkyl radical contains 1to 2 carbon atoms, and

(2) 0.01 to 10% by Weight of 2,2'-dipyridylamine.

2. The composition of claim 1 wherein the salt is a mixed salt of analkyl primary amine having 8 to 30 carbon atoms andmoonchloromethylphosphonic acid.

3. The composition of claim 1 wherein the phosphonic acid ismonochloromethylphosphonic acid.

4. The composition of claim 1 wherein the synthetic ester lubricatingoil comprises esters of monocarboxylic acids having from 4 to 12 carbonatoms and pentaerythritol.

5. The composition of claim 1 wherein the synthetic ester lubricatingoil comprises a mixture of from to by weightbis(2,2,4-trirnethylpentyl)azelate and 20 to 50% by Weight1,1,1-trimethyl propane triheptanoate.

6. A lubricant additive composition consisting essentially of (1) a saltof an alkyl amine selected from the group consisting of alkyl primaryand alkyl secondary amines having from 8 to 30 carbon atoms and a monotoper-haloalkyl phosphonic acid, wherein the haloalkyl radical contains 1to 2 carbon atoms, and

(2) 2,2-dipyridylamine, the weight ratio of (1) to (2) being from about0.01/1 to about 10/1.

References Cited by the Examiner UNITED STATES PATENTS 2,559,754 7/1951Bittles et al. 25232.5 X 2,683,691 7/1954 Thorpe et al. 252-32.52,777,319 1/1957 Williams et al. 25232.5 3,121,691 2/1964 Eickemeyer2525O X 3,126,344 3/1964 Matuszak et a1 25256 X OTHER REFERENCES Barneset al.: Synthetic Ester Lubricants, Lubrication Engineering, Aug. 1957,pages 454-45 8.

DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner.

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR AMOUNT OF A SYNTHETICESTER LUBRICATING OIL AND (1) 0.01 TO 5% BY WEIGHT OF SALT OF AN ALKYLAMINE SELECTED FROM THE GROUP CONSISTING OF ALKYL PRIMARY AND ALKYLSECONDARD AMINES HAVING 8 TO 30 CARBON ATOMS AND A MONO- TOPER-HALOALKYL PHOSPHONIC ACID, WHEREIN THE HALOALKYL RADICAL CONTAINS 1TO 2 CARBON ATOMS, AND (2) 0.01 TO 10% BY WEIGHT OF2,2''-DIPYRIDYLAMINE.